Facebook remained the most popular social networking destination among U.S. adults, but users are also turning to other websites for their daily social fix .

Social networks are used by 73 percent of U.S. users above the age of 18, according to a study released on Monday by the Pew Internet and American Life Project on Monday. The study was based on 1,801 adults interviewed from August 7 to Sept. 16 this year.

Facebook was the dominant social networking site, boasting an audience of 71 percent of online U.S. adults, growing from 67 percent late last year.

While Facebook was a universal favorite, some 42 percent of online adults used multiple social networking sites, the study said. Pinterest attracted women, Twitter and Instagram were heavily used by young adults, African Americans and city dwellers, and LinkedIn was favored by college graduates, older users and high-income households.

Usage of all Facebook alternatives grew, according to the survey. LinkedIn was used by 22 percent of U.S. adults online, Pinterest by 21 percent, Twitter by 18 percent and Instagram by 17 percent.

The engagement levels varied, with 63 percent of Facebook users visiting the website at least once a day, and 40 percent visiting multiple times. Instagram, which is owned by Facebook, had 57 percent of users visiting once a day and 35 percent logging in multiple times. Around 46 percent of Twitter users visited at least once, and 29 percent multiple times.

Once viewed as a social networking platform for college students, Facebook is now attracting a larger number of Internet users aged 65 or more, according to the survey. Facebook is used by around 45 percent of U.S. Internet users aged 65 or more, growing from 35 percent late last year.

Twitter and Instagram are becoming more popular among African Americans and users aged 18 to 29. Around 34 percent of African American Internet users in the U.S. adopted Instagram, growing from 23 percent last year. The site was used by 37 percent of users aged between 18 and 29, growing from 28 percent in the comparable period last year.

Women "are four times as likely as men to be Pinterest users," the survey said. Pinterest was used by 33 percent of women and 8 percent of men interviewed for the survey.

The Pew survey does not include information related to usage of sites such as Google+, Tumblr, Reddit and Vine.